In general, a hybrid vehicle or an electric vehicle is operated by an electric motor (hereinafter referred to as a “drive motor”) generating torque using electrical energy.
A hybrid vehicle may operate in an electric vehicle (EV) mode in which only the torque of the drive motor is used, and may operate in a hybrid electric vehicle (HEV) mode in which both the torque of the engine and the torque of the drive motor are used. The electric vehicle operates using the torque of the drive motor.
Most drive motors used as power sources for vehicles are permanent magnet synchronous motors (PMSM). The performance of a permanent magnet is maximized to obtain the greatest output from the PMSM in a limited layout condition.
In a permanent magnet, a neodymium (Nd) constituent improves the strength of the permanent magnet, and a dysprosium (Dy) constituent improves high temperature demagnetization endurance. However, such rare earth metal (Nd and Dy) constituents of the permanent magnet are deposited in limited countries, such as China, are very expensive, and have significant price fluctuations.
In view of this, induction motors have been studied, but the application of induction motors has limitations in that an excessive increase of volume and weight may be required to output the same motor performance.
In recent years, development of a wound rotor synchronous motor (WRSM) as a drive motor to be used for a power source of the vehicle has been undertaken to replace the PMSM.
The WRSM has a coil that is wound, not only on a stator, but also on a rotor for electro-magnetizing the rotor when a current is applied to the rotor to replace the PMSM.
In the WRSM, the rotor is spaced apart from the stator by a predetermined gap, and a magnetic flux is generated by applying a current to a rotor coil through a brush and a slip ring.
The rotor coil is wound around the rotor core. The rotor core is combined with a rotation shaft. The slip ring is mounted to one portion of the rotation shaft. The brush contacts the slip ring integrally rotating with the rotation shaft, and applies a DC current to the rotor coil.
The slip ring is electrically connected to the rotor coil through a fusing terminal. The fusing terminal is compressed by a fusing machine in a state of supporting a positive connection terminal and negative connection terminal of the rotor coil, and is welded to the rotor coil by resistance welding.
A sufficient insulation distance must be secured between the fused portion connecting the fusing terminal to the connection terminal of the rotor coil and a coil winding portion wound by the rotor coil.
In addition, a sufficient working space in which parts of the rotor do not interfere with the fusing machine must be secured in order to fuse the fusing terminal and the connection terminal of the rotor core using the fusing machine.
In order to secure the sufficient insulation distance and the sufficient working space, an entire length of the drive motor is unavoidably increased.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.